In 1985 the NIDR conducted a national survey of the oral health status of employed adults and seniors, in which measurements of root caries were made for the first time on a national sample of the U.S. population. Examinations were made on 15,132 employed adults representing 99.6 million persons. Previous reports of the distribution of root caries vary widely, which may be related to how root caries was defined or measured. For the survey, visual tactile examination were made for decayed and filled root surfaces. Each tooth was considered to have four root surfaces. No x-rays were taken. Approximately 21% of the employed dentate population aged 18-64+ years had at least one decayed (D) or filled (F) root surfaces (S) with more males than females affected. The mean number of DFS was less than one for the employed dentate population. Less than half (47%) of the DFS were filled. Distribution of the disease by tooth and surface type was analyzed. Buccal surfaces were the most frequently affected surfaces with decay or fillings occurring four times as often here as on any other surface. The distal and mesial surfaces are the next most frequent sites of root caries and the lingual surface is the least effected. However, the differences among these last three surface types is minimal. Root caries was most common in mandibular pre- molars, molars and maxillary cuspids. Lower incisors were rarely involved (<1% of the DFS occurred in these teeth).